As fuel prices continue to rise, reducing fuel consumption is becoming more important in, for example, the construction market. For example, it is important in North America and especially important in regions of the world such as, for example, India, to name just two regions. Due to increasing fuel prices and demands to improve overall vehicle efficiency, manufacturers are being asked to find new methods to reduce the hydraulic power consumed during operation. Many of these solutions are relatively high cost and complex systems such as load-sensing valves and variable-displacement pumps. Those systems are also relatively sensitive to contamination-related problems.
There are hydraulic systems which use open-center valves and fixed-displacement gear pumps. An open-center valve has a neutral position that allows fluid to flow continuously through the valve, as opposed to a closed-center valve which blocks fluid from flowing through the valve in its neutral position. Hydraulic systems that use open-center valves and fixed-displacement gear pumps tend to be relatively simple, cost effective, and contamination tolerant.
However, such systems tend to be inefficient. A significant amount of power is wasted by running the full pump flow through open-center valves when the flow is not needed.